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Evaluation of the stress response in healthy ...

Description

Citation

Evaluation of the stress response in healthy juvenile rainbow trout after repetitive intermittent treatment with chloramine-T or formalin

Author(s)

J. G. Sanchez, David J. Speare, G. J. Johnson, Barbara S. Horney

Journal

Journal of Aquatic Animal Health

Date

1997

Volume

9

Issue

4

Start page

301

End page

308

Abstract

Tanks of healthy juvenile rainbow trout (Oncorhynchus mykiss) were exposed to chloramine-T (10 mg/litre; 40 fish) or formalin (200 mg/litre; 40 fish) for 1 h once per week for 4 weeks. The effect of this treatment on the primary stress response was evaluated by measuring circulating cortisol levels with a radioimmunoassay technique. Blood cortisol levels were analysed at 1, 24, and 96 h after each treatment and compared with pre-exposure baseline values and with values obtained from sham-treated fish. At 1 h, fish in all treatment categories had elevated cortisol levels compared with baseline values, but values in those fish treated with chemicals were no different from those that were sham treated. Cortisol levels returned to near baseline by 24 h after treatment. In a second experiment, the effect of twice weekly 1-h exposure to chloramine-T (10 mg/litre) on secondary stress indices of rainbow trout was probed during an 11-week growth trial by measuring haematocrit, plasma glucose, sodium, and chloride levels in treated, untreated, and sham-treated fish. No evidence of a secondary stress response could be detected in fish treated with chloramine-T when they were compared with either control group. It is concluded that intermittent exposure to chloramine-T at 10 mg/litre does not elicit a primary or secondary stress response in rainbow trout and that stress is not the mechanism responsible for growth deceleration in treated fish..